Carrier-signaling system



March 23 1926.

'3. WHITE CARRIER SIGNALING SYSTEM Filed Sepic 5, 1925 UNITED STATESPATENT OFFICE.

CHARLES WHITE, OF VEST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEC-TRIO COMPANY, INCORPORATED, 01 NEW YORK, N. Y., A CORPORATION OF NEWYORK.

,CARBI ER-SIGNALING SYSTEM.

Application'filed September 5, 1923. Serial No. 661,008.

To all whom it may concern:

Be it known that 1, CHARLES \Vnrrn, a citizen of the United States ofAmerica, residing at West Orange, in the county of I? and State of NewJersey, have invented certain new and useful Improvements inCarrier-Signaling Systems, of

' which the following is a full, clear, concise,

and exact description.

This invention relates to a carrier signaling system.

According to the ordinary practice in multiplex carrier wave telephonesystems the transmission and receiving branches at each end of each highfrequency channel of the system are coupled to low frequency circuits orlines terminating locally or extending to distant stations.

The low frequency circuits or lines may be two-way circuits whereinsignals are transmitted in opposite directions over the same circuits ortwo one-way circuits in which the signals are transmitted in onedirection over one circuit and in the opposite direction over the othercircuit.

A two-way low frequency circuit, ordinarily known as a two-way circuitis coupled to a transmitting branch and associated receiving branch of ahigh frequency channel by means of a hybrid coil and associated lowfrequency line balancing network.

The two one-way low frequency circuits, commonly known as a four-wirecircuit, are ordinarily connected one to a transmitting branch and theother to the associated receiving branch of the high frequency receivingchannel.

Some of the channels of the multiplex carrier telephone system may beterminated in two-wire low frequency circuits and others in four-wirecircuits. Furthermore, one end of a high frequency channel may beterininated in a two-wire circuit and the other end in a four-wirecircuit.

Depending upon service conditions, a'high frequency channel of such amultiplex carrier telephone system may for a period of time be coupledto a two-wire circuit and for another period to a four-wire circuit.Furthermore, it is frequently desirable to quickly effect a change inthe character of t e minat n f 09s 9 2? 9? th hi h frequency channels ofa multiplex carrier telephone system.

This invention contemplates switching arrangements by which such achange in carrier channel termination may be quickly effected. l

Another feature of the invention relates to the provision of signalreceiving apparatus which may be associated with either a two-wire or afour-wire circuit and the high frequency channel with which theappropriate low frequency circuit is coupled;

The apparatus and circuits illustrated in the drawing represent thatrequired at a terminal station of a multiplex carrier telephone system.

As is well known, a multiplex carrier telephone system comprises a highfrequency main line terminating at each end in a plurality oftransmitting and receiying branches. The transmitting and receivingbranches are associated in pairs and coupled to terminating lowfrequency circuits or lines. Carrier currents of different frequenciesare employed for the different channels of the system. In the particularsystem illustrated, the carrier frequencies for transmission in onedirection are comprised within a frequency range entirely different fromthat of the frequencies employed for transmission in the oppositedirection.

For. the purpose of the present invention, it is not necessary todisclose an entire multiplex carrier telephone system but only theapparatus required at one of the terminal stations thereof.

lhe portion of the system illustrated in the drawing comprises a highfrequency main line ML coupled by means of transformers TT and RT to thetransmitting and receiving branches of the various chan nels of thesystem.

A single high frequency transmitting branch TU is shown in detail whilethree others, T6 TC 'and TC are indicated."

likewise, one receiving branch RG is shown in detail while three others,RC RC, and, RC, are indicated. i

The various transmitting branches are similar except as to thedifference in the constants required due to the different freqieaer teier c rren t.)

channels, so that a description of one transmitting branch will sufiic.

The transmittingbranch includes a niodulator hi to which carrier currentof the frequency assigned to the channel is supplied from an oscillatorC and a transmitting iand filter TBF, v

The modulator M, may be of any well known type, such, for example, as anelectronic valve of the type disclosed in Fig. 42 of the articleentitled Carrier current telephony and telegraphy by Colpitts andBlackwell, published in the Transactions of the American institute ofElectrical Engr neers, Vol. 4.0, 1921.

The transmitting band filter TEE, which may be of the type disclosed inU. S. patent to Campbell, No. 1,227,113, May 22, 1917, is designed topass currents of the carrier frequency assigned to the channel and ofthe frequencies within the upper or lower side band thereof and tosuppress currents of all ther frequencies.

The receiving branches are alike except as to the constants of some ofthe apparatus thereof due to he different carrier frequen cies employedin the different channels. Consequently, a description of one suchbranch will suffice.

The receiving branch RC, includes a receiving band filter RBF,. ademodulator DM an amplifier A a low pass filter LPF,, a high pass filterHPF, and a rectifier R The receiving band filter RBF,, of the typedisclosed in the Campbell patent supra, is designed to pass currents ofthe carrier frequency assigned to the channel and of the frequencieswithin the upper or lower side band thereof and to suppress currents ofall other frequencies.

The demodulator, amplifier and rectifier may be of any well known type,such as the electronic valve type disclosed in Fig. 42 of the Colpittsand Blackwell article supra.

The low pass filter LPF of the type 'dis closed in id Campbell patent,is designed to pass currents of frequencies below tlu upper limit of thevoice range and suppress currents of higher frequencies. The high passfilter, also of the type disclosed in the Campbell patent, is designedto pass currents above the upper limit of the voice range and tosuppress currents of lower frequencies; I

The input of the transmitting branch TC, and the output of the receivingbranch RC may be terminated in a two-wire low frequency circuit or afour-wire low frequency circuit.

In order that the termination of the transmitting and receiving branchesof a high frequency channel may be readily and quickly changed,switching apparatus for this purpose is provided.

This switching apparatus comprises eavers switches H5 HS HS, and HS Whenthese switches are in the position shown in full lines, the transmittingbranch TC is connected to one of the one-way circuits C and thereceiving branch RC is connected to the one way circuit C These two oneway circuits together form a four-wire low frequency terminatingcircuit.

When the switches are in their dotted line positions, the transmittingbranch TC, and receiving branch RC, are coupled to a two-wire lowfrequency terminating circuit C, by means of hybrid coil 1 and itsassociated low frequency balancing network if. The hybrid coil and itsassociated balancing network serve to conjugately relate the transmitting and receiving branches with respect to the connected two-wirelow frequency terminating circuit.

Some two-wire low frequency terminating circuits extend to stationsequipped for transmitting thereover 16 cycle signaling current, whileothers extend to stations equipped for transmitting thereover 135 cyclesignaling current. Usually, the stations in which the distant end of thefourwire low frequency circuits terminate are equipped to transmitthereover 135 cycle signaling current.

It is, therefore, necessary that the signal receiving and transmittingapparatus atthe carrier terminal station connected to the system be of atype suitable to receive and transmit signaling current of the properfrequency.

Therefore, at the terminal station there is provided a source 2 of 16cycle signaling current and a source 3 of 135 cycle signaling current.There is also provided a receiving relay 4 responsive to the 16 cycleringing current and a signal receiving relay 5 re sponsive to the 135cycle signaling current transmitted from the respective distant stationsover their connecting two-wire low frequency lines or circuits. Relay 5is also responsive to 135 cycle signaling current transmitted over a atwire circuit from a dis tant station.

Switches VS, and HS control the connection of the proper receiving relayto the connected terminating circuit and switches VS, control theconnection of the proper source of signaling current to the connectedterminating circuit. The switches V8,, VS, and HS, are shown in theirfull line position connecting the proper receiving relay and source ofsignaling current to the four-wire terminating circuit.

The operation of the system as shown and as thus far described is asfollows he 135 cycle signaling current incomi over the low frequencycircuit C actuates relay 5 which opens its contact, releasing relay 6The closure of the contact of relay- 6 short-circuits the frequencydetermining circuit of oscillator 0 so that the flow of carrier currentover the main line from the terminal station is interrupted.

When a signal is incoming over the highfrequency main line ML asindicated by the cessation of flow of the carrier current, relay '4' inthe output circuit of rectifier ll, releases, causing the lighting of asignal lamp 8 and the operation of relays 9 and 10. Relay 9 connects thesource 3 of 135 cycle signaling current to the low frequency circuit CRelay 10 closes .its upper contact thereby short-circuiting a winding ofthe hybrid coil 1 and pr venting singing during the ringing operation.

When it is desired to terminate the transmitting and receiving branchesTC, and EC, in a two-wire low frequency circuit equipped withtransmitting and recelvmg signal apparatus of the 135 cycle type, theswitches HS H8 H3 HS and H8 are moved to their dotted line positions andswitches VS and VS are left in their full line position. The 135 cyclesignaling current incoming over low frequency C11C111l7 C actuatesreceiving relay 5 as before, causing the release of relay 6 so thattransmission of carrier current over the main line is interrupted. I

When a signal incoming over the high frequency line is indicated by theinterruption of the flow of carrier current thereover, relay 7 releasesas before, causing lamp 8 to light and relays 9 and 10 to operate. Relay9 connects 135 cycle ringing current from source 3 to the low frequencycircuit.

Relay 10 functions as before, shortcircuiting the winding of the hybrid(,Oll l. It also opens its lower contact thereby disconnecting relay 5from the low frequency circuit during the ringing operation.

It is assumed that low frequency line C is equipped at its distant endWithapparatus for transmitting 16 cycle rmgmg current and with signalreceiving apparatus responsive to 16 cycle ringing current transinittedfrom the carrier terminal station.

When the transmitting and receiving branches of the high frequencychannel are to be terminated in the two-wire low frequency line orcircuit C, switches H HS; and HS, remain in their dotted line positions,switches VS, and VS, are moved to their dotted line position and switchHS, is moved to connect to the terminals of the low frequency line OSwitch HS may be in either of its positions.

The 16 cycle signaling current incoming to the carrier terminal stationover low frequency circuit C, actuates relays: which releases relay 6thereby interrupting the flow of carrier current over the main line.

Ringing signals incoming over the main line, as indicated by the absenceof carrier current therefrom, release relay *3 wheresuch channel ineither fouuwirc or a two wire low frequency line and for connecting theproper signaling apparatus to the connected terminating circuit, it isto be understood, of course, that hothends of ahigh frequency channelmay be similarly equipped and both ends or one end only of all otherchannels may be similarly equipped.

The rectifier relays of the other receiving branches RC RC and RC, areindicated by relays 17, 27 and 37. Each of these relays controls a lampsimilar to 8 and relays similar to 9 and 10 associated with theirrespective receiving branches. The operating circuit for relays 9, l0and lamp 8 in- 1? cludes the normally open contact of relay 7 and thenormally closed contact of one of the relays 17, 27 or 37." Thesenormally closed contacts normally short-circuit resistance 38 and relay39 so that so long as one of the relays 7, 17, 2'? and 37 is energized,relay 89 will not operate. However, when all of these relays 7, 17, 27and 37 are re leased as would be the case upon a failure of the mainline ML, relay 39 would then operate to close the circuit of an alarmsignal 40. The combined resistance of relay 39 and resistance element 38is so great, however, that when included in circuit with relays 9 and 10of receiving branch RC, and the similar relays of the other receivingbranches which are now all connected in parallel, the amount of currentreceived by each of such parallel connected relays is insufficient tocause the operation thereof. Therefore, no signaling current isconnected to any of the low frequency terminating cir' cuits when thehigh frequency line fails, but an alarm signal is given.

The circuit including relays 9, 10 and lamp 8 ray also include a switch11 whereby this circuit may be opened should the oscillator at thedistant terminal. supplying carrier current received by receiving branchRC fail for any reason. The other receiving branches may be similarlyequipped.

The invention set forth herein is of course, susceptible of variousother modifications and adaptations.

The invention claimed is:

1. In a signaling system, a carrier wave channel terminating .in atransmitting branch and a receiving branch, a two-Wire low frequencycircuit, a four-wire low frequency circuit, two sources of low frequencyRel ay 7 Kill signaling current of respectively difierent character, twolow frequency signal receiving branches and two-Way switches which, whenin one position connect the two-Wire low frequency circuit to thetransmitting and receiving branches and to one of said sources of lowfrequency signaling current and one low frequency signal receivingbranch and, when in the other position, connect the four-Wire lowfrequency circuit to the transmitting and receiving branches and to onelow frequency signal receiving branch.

2. In a signaling system, a carrier Wave channel terminating in atransmitting branch and a receiving branch, a two-Wire low frequencycircuit, a tounwirc low frequency ci1cuit, sig11al receiving apparatus,and two-position switches which When in one position connect thetwo-Wire low fre quency circuit to the transmitting and receivingbranchesancl the signal receiving apparatus to the connected lowfrequency circuit and when in the other position connect the founwirecircuit to the transmitting and receiving branches and the signalreceiving apparatus to the incoming leg of the four-Wire circuit.

In Witness whereof, I hereunto Subscribe ny name this 29th day of AugustA. 1)., 30

0 HA R LES XVI-UTE.

